Protease is an enzyme which catalyzes hydrolysis of peptide bond in proteins or peptides, exists in all organisms and plays a variety of physiological roles. Most of proteases from microorganisms are secreted to the extracellular environment and their activities are inhibited or activated by carbon sources or nitrogen sources. In addition, most of microbial proteases have their origin to pathogenic microbes to animals or plants, or the proteases have a pathogenic property.
Microbial proteases are classified according to such characteristics as temperature, optimal pH, and the residues at the active site and have different industrial applications accordingly. For example, proteases are classified into thermostable, mesophilic or thermophilic based on temperature; into acidic, weak acidic, neutral or basic based on optimal pH; and into serine protease, cysteine protease, aspartate protease or metalloprotease based on the residues at the active site.
The enzymatic activity of proteases is regulated by metallic cations such as Ca2+, Zn2+, Mg2+, Mn2+ found at the active site of the enzymes. Most proteases are zinc-containing proteins in which zinc is essential for activity. The representative example for the protease is serrapeptase produced by Serratia marcescens(ATCC 21074) isolated from the intestine of Bombyx mori and this enzyme can be used as an anti-inflammatory agent because it has a fibrin degrading ability and a hydrolysis activity for bradykinin and histamine which are inflammatory peptides. Bacterial proteases which have been cloned and characterized hitherto include those derived from Vibrio proteolyticus (See, David, V. A., A. H. Deutch, A. Sloma, D. Pawlyk, A. Ally, and D. R. Durham. Gene. 112:107-112. 1992), Erwinia chysanthemi B374 prtA (See, Ghigo, J. M., and C. Wandersman. Mol. Gene. Genet. 236:135-144. 1992), Psudomonas aeruginisa LasB (See, Doung, F., A. Lazdunsk, B. Cami, and Murgier. Gene. 121:47-54. 1992), Serratia marcescens PrtSM (See, Braunagel, S. C., and M. J. Benedik. Mol. Gen. Genet. 222:446-451 1990), Bacillus thuringiensis (See, Lovgren, A., M. Zhang, A. Engstrom, G. Dalhammar, and R. Landen. Mol. Microbiol. 4:2137-3146. 1990), etc.